Music therapy is an interpersonal process which uses music and all of its physical, mental, social, aesthetic, and spiritual qualities to help improve, restore or maintain health. The supportive role of music therapy in cancer rehabilitation has been shown to facilitate social interaction, nurture feelings of community and help to draw individuals out of their isolation and into a shared experience. Within the field of cancer care a large amount of music therapy practice and research has been conducted with cancer patients in the final stages of their illness. The majority of research to date in this area has either been of a qualitative or quantitative study design with very few mixed methods qualitative/quantitative research studies conducted. The objective of this doctoral research study is to investigate in depth the lived experience, perceptions and effects of an eight week group improvisational music therapy intervention with fifteen women recently diagnosed with breast cancer. The project presented in this thesis is informed by a pilot study conducted by the author in the UK. It forms an integral component of this doctoral thesis. The pilot study used a mixed methods research approach to investigate the effects of both listening to music for relaxation and music improvisation (the playing of tuned and untuned percussion instruments) amongst twenty‐nine non‐homogenous cancer patients at a cancer help centre. This doctoral research investigates the music improvisation component of the pilot study in more depth, adopting a similar mixed methods research approach (with the addition of further qualitative methods and quantitative measures) in order to investigate the lived experience and the effects of the intervention on the women in this study. The qualitative findings presented here reveal and explain how group improvisational music therapy provided a safe haven in which the fifteen women participants experienced identity, support, bonding, group cohesion and distraction from their breast cancer. The participants further experienced empowerment through choice and confidence building offered by music therapy. The women’s perceptions of the differences between their conventional medical care and the group improvisational music therapy experience are also described. The quantitative psychosocial three time point measures, though not significant, indicate improvement in the women’s levels of anxiety and depression, coping skills and overall quality of life at the end of the eight week intervention. The pre/post intervention psychological data provide statistical evidence of improved mood states which are further supported by the analysis of the qualitative data. Physiological measures of salivary immunoglobulin A and cortisol appear altered with a significant decrease in salivary cortisol. Both the pilot and this doctoral study suggest a link between positive emotions and the immune functioning of cancer patients. The doctoral study more specifically illuminates the lived experience and perceptions of women recently diagnosed with breast cancer as a result of being involved in group improvisational music therapy. The findings of this research will help inform future research and music therapy practice as well as provide a more holistic understanding of the effectiveness of music therapy with cancer patients. The benefits of group improvisational music therapy described here are such that music therapy should be made widely available as a valuable part of the management of women recently diagnosed with breast cancer.